In the integrated circuit manufacturing process, integrated circuit devices, such as transistors, are first formed at the surface of a semiconductor substrate. An interconnect structure is then formed over the integrated circuit devices. Metal connectors are formed over and electrically coupled to the interconnect structure. A passivation layer and a polymer layer are formed over the metal connectors, with the metal connectors exposed through the openings in the passivation layer and the polymer layer. A molding compound is formed aside the semiconductor substrate. A redistribution circuit structure is then formed over the molding compound and the polymer layer, which includes redistribution lines connected to the metal connectors.
Since a height difference is present between the polymer layer and the molding compound, the redistribution lines of the redistribution circuit structure formed thereover may be easily broken during temperature cycling. Therefore, there are many challenges related to configuring the redistribution line with a fine width and/or a thin thickness.